Standard switching type (B-type) makes valves on/off by switching circuit with outputing active contacts signal to show a fully open or fully closed state of valve. Smart modulating type (A-type) realizes intelligent regulation and control through receiving a standard output signal 4-20mA.DC, 0-10V.DC or 1-5V.DC from computer or industrial instrument as well as outputs 4-20mA.DC standard feedback signal. Operating time from 7s to 100S
